1. Field
Example embodiments of the inventive concepts relate to semiconductor devices.
2. Description of the Related Art
A complementary metal oxide semiconductor (CMOS) image sensor (CIS) is an element that converts an optical image into an electrical signal using CMOS fabrication technology. The CIS includes a number of metal oxide semiconductor (MOS) transistors equal to the number of pixels and sequentially detects outputs of the pixels using the MOS transistors. Using this switching method, the CIS converts signal electrons generated by the reaction with light into voltages and realizes image information through a signal processing process.
A typical image sensor may include photodiodes formed under a surface of a substrate, and logic circuits formed on the substrate. That is, the image sensor has a front illumination structure in which light is irradiated from an upper surface of the substrate.
In addition, a backside illumination (BSI) image sensor can be used. The BSI image sensor can minimize a step difference on a light-receiving unit by receiving light through the back of a wafer and eliminate the interference of light due to metal routing.
A bonding technology for implementing a BSI image sensor is classified as an oxide-to-oxide process and a metal-to-metal process, and a through silicon via (TSV) or a back via stack (BVS) technology applied to these processes is drawing a lot of attention.
In the TSV or BSV technology, an isolation structure may be formed between a plurality of terminals (e.g., through electrodes) in order to suppress the generation of leakage current. However, when a defect occurs in part of the isolation structure, the leakage current can still be generated.